1. Field of the Invention
The invention, according to the various embodiments described herein, relates to a digital/analog converter which provides a very high dynamic range and a unit for direct digital synthesis (DDS) with such a digital/analog converter.
2. Discussion of the Background
In communications systems, it is necessary to generate broadband signals with a high dynamic range. For this purpose, high-speed digital/analog converters are generally fitted with a return-to-zero unit (return-to-zero (RTZ)) which minimises the effects of settling processes on the output signal. In order to create a digital/analog converter which provides a good signal-to-noise respectively distortion ratio (signal-to-noise and distortion ratio (SNDR)), a slight phase noise in these return-to-zero units is necessary. For optimal operation in this context, the lowest possible residual jitter, in the order of magnitude of, for example, a few femtoseconds, should be aimed for, which can be achieved only with narrow-band oscillators of extremely high quality and is associated with high costs.
The disadvantage is that the digital/analog converter uses a complex clock distribution including time deskewing (deskewing). Numerous intermediate amplifiers and phase shifters are used in these clock distribution systems to distribute the clock pulse and achieve the required driver capability. In this context, technologically determined fluctuations in delay time must be compensated. Each of these components adds additional jitter, which impairs the accuracy of the time system, that is, of the digital/analog converter, especially with high sampling rates.